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Inorganic Nitrate Supplementation in Young and Old Obese Adults Does Not Affect Acute Glucose and Insulin Responses but Lowers Oxidative Stress

Lookup NU author(s): Ammar Ashor, Shakir Chowdhury, Dr Clio Oggioni, Othman Qadir, Dr Kirsten Brandt, Abbas Ishaq, Professor John Mathers, Dr Gabriele Saretzki, Dr Mario Siervo

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Abstract

Background: Aging and obesity are associated with raised oxidative stress and a reduction of nitric oxide (NO) bioavailability, with subsequent decline in insulin sensitivity and endothelial function. Inorganic nitrate is converted into NO via a 2-step reduction process and may be an effective nutritional intervention to modify vascular and metabolic functions.Objectives: This study tested whether inorganic nitrate supplementation improved glucose disposal and attenuated the acute effects of hyperglycemia on oxidative stress, inflammation, and vascular function in young and old obese participants.Methods: Ten young (aged 18-44 y) and 10 old (aged 55-70 y) obese participants consumed 75 g glucose followed by either potassium nitrate (7 mg/kg body weight) or potassium chloride (placebo) in a randomized, double-blind crossover design. Resting blood pressure (BP), endothelial function, and blood biomarkers were measured for 3 h postintervention. Biomarkers included plasma nitrate/nitrite (NOx), glucose, insulin, cyclic GMP, interleukin 6, 3-nitrotyrosine, E- and P-selectins, intercellular adhesion molecule 3 (ICAM-3), and thrombomodulin, as well as superoxide in freshly isolated peripheral blood mononuclear cells (PBMCs).Results: Inorganic nitrate supplementation did not affect plasma glucose (P =0.18) or insulin (P =0.26) responses. The increase in plasma NOx concentrations 3 h after the administration of inorganic nitrate was significantly higher in young than in old participants (234% increase compared with 149% increase, respectively, P < 0.001). Plasma 3-nitrotyrosine concentrations declined significantly after inorganic nitrate supplementation compared with placebo (3 h postdose, 46% decrease compared with 27% increase, respectively, P=0.04), and a similar nonsignificant trend was observed for superoxide concentrations (3 h postdose, 16% decrease compared with 23% increase, respectively, P=0.06). Plasma cyclic GMP, ICAM-3, and thrombomodulin concentrations differed between young and old participants (P < 0.01). Inorganic nitrate supplementation did not improve BP or endothelial function.Conclusions: Oral supplementation with inorganic nitrate did not improve glucose and insulin responses but reduced oxidative stress in old individuals during acute hyperglycemia. This trial was registered at www.controlled-trials.com as ISRCTN42776917.


Publication metadata

Author(s): Ashor AW, Chowdhury S, Oggioni C, Qadir O, Brandt K, Ishaq A, Mathers JC, Saretzki G, Siervo M

Publication type: Article

Publication status: Published

Journal: Journal of Nutrition

Year: 2016

Volume: 146

Issue: 11

Pages: 2224-2232

Print publication date: 01/11/2016

Online publication date: 12/10/2016

Acceptance date: 08/09/2016

ISSN (print): 0022-3166

ISSN (electronic): 1541-6100

Publisher: American Society for Nutrition

URL: http://dx.doi.org/10.3945/jn.116.237529

DOI: 10.3945/jn.116.237529


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